Quantum entanglement is a very important phenomenon since it is proposed by Einstein, Podolsky and Rosen [1]}, Schrodinger [2]} and Bell [3]}. The nonlocality and the coherence of quantum entangled systems makes them have important applications in quantum information, such as in quantum teleportation [4]} (for experimental realization see [5]}), quantum cryptographic schemes [6]}, dense coding [7]} and quantum parallel computation [8]}. The quantifying of the quantum entanglement degree of bipartite pure states has been well done [9]}, but how to define and quantify other complex systems' quantum entanglement degree is still a very hard problem [10]}.
